This invention has to do with corrosion, erosion and wear resistant alloy structures, and methods therefor. More particularly, the invention relates to more economical diffusion coating of alloys having as base metals iron, cobalt and nickel, while obtaining benefits of increased resistance to corrosion characteristic of rhodium or platinum ternary alloys, e.g. with aluminum and the alloy base metal.
The invention is further concerned with improvements in specific properties of such ternary alloy systems by the incorporation of discrete particulate matter, such as alumina, or a hard carbide such as tungsten carbide for their specific erosion or wear characteristic. Remarkably, the use of the discrete particulate matter enables reductions in the quantity of rhodium or platinum precious metal needed to form a diffusion coated case of adequate depth on the alloy structure being treated, so that the addition of the erosion and wear properties resulting from incorporation of the mentioned discrete particulate matter, has the further and unexpected benefit of lowering the precious metal requirement and thus the material casts of the product, enabling a widely improved product at lower cost.
In the production of diffusion alloy coatings such as are employed on high performance metal parts, including turbine vanes and blades, pump parts, and other parts subject to unusual demands for erosion, corrosion and wear resistance it is desirable to produce such coatings on a wide variety of structures, by which term herein is meant a shaped article in an intermediate or final configuration for its intended use, to do so rapidly and repeatably so as to obtain superior performance. The incorporation of various discrete interdispersed phase-forming materials into diffusion coatings enables obtention of individually tailored properties responsive to the selective inclusion, in a controlled interdispersion, of refractory oxide, nitride or hard carbide material and/or elemental metal additives, which are kept and remain interdispersed, i.e. remain as discrete particulate material in the interdiffusion layer, with a high degree of control as to location, concentration, and, thereby, as to properties of the final product.